1. Field of the Invention
The present invention relates to a propulsion device; and is particularly directed to a hydrodynamic propulsion device possessing an expansion chamber which is located downstream of a cross-sectional widening of an interior passage for the inflow of a medium which is to be expelled through a discharge nozzle.
2. Discussion of the Prior Art
A propulsion of the type mentioned hereinabove is already known from the disclosure of German Patent No. 34 35 076, as being in the form of a device in the nature of a water-piston or water-column engine, in which periodically generated reaction gas bubbles separate out in a nozzle conduit a portion of the inflowing mass of water, and then eject the portion of the water mass in opposition to the supportive action of an intermittently-operating nozzle. Although this valveless and consequently low-frictionally operating propulsion concept has proven itself capable for high propulsion outputs over short periods of time, notwithstanding the therewith encountered unsteady operating cycles, nonetheless, for the practical use thereof, it evidences a number of disadvantages which result from the discontinuous or intermittent mode of operation. Above all, belonging to these disadvantages are the high levels of noise which are developed and the intense mechanical stresses to which the structure is exposed as a result of the frequent load fluctuations. Moreover, the theoretically attainable degree of efficiency of such a water-piston engine, in actuality, is noticeably reduced due to the fact that comparatively lengthy so-called dead operating periods must be taken into consideration between the ejection of a portion of a water column and the filling of the conduit with the inflow through the nozzle.